Title

Identifier

Author

Degree

Master of Science (MS)

Department

Mechanical Engineering

Document Type

Thesis

Abstract

Buckling of a stiffened composite cylinder is a very complex phenomenon that involves complex interactions between the skin and the stiffeners. Depending on different configurations of the skin and stiffener, different buckling failure modes and failure loads are observed in stiffened cylinders. In this work failure modes and buckling loads of stiffened composite cylinders under uniaxial loading condition is investigated by using analytical and experimental approaches. In the first Chapter an improved smeared method is developed to model the buckling problem of an isogird stiffened composite cylinder. In this model the stiffness contributions of the stiffeners is computed by analyzing the moment and force effect of the stiffener on a unit cell. Then the equivalent stiffness of the stiffener/shell panel is computed by superimposing the stiffness contribution of the stiffeners and the shell. Once the equivalent stiffness parameters are determined for the whole panel, the buckling load is calculated using the energy method. A 3-D finite-elements model was also built which takes into consideration the exact geometric configuration and the orthotropic properties of the stiffeners and the shell. Based on the finite-elements model a discussion was made on the different buckling failure modes observed. A limited experimental analysis was also performed to compliment the two analytical methods used to determine the buckling load of the stiffened cylinder. Results of the three types of analysis methods are compared, and comments made on the reliability of the analytical models developed. Finally a parametric study was carried out and general conclusions were drawn regarding the optimum configurations of the different parameters of the grid-stiffened cylinder.